A method of non-invasively measuring venous oxygen saturation, comprising: applying a pressure transducer at a first site on a body, applying a drive signal to the external pressure transducer at a predetermined frequency, to cause a series of pulsations of a predetermined magnitude in the venous blood...http://www.google.de/patents/US7263395?utm_source=gb-gplus-sharePatent US7263395 - Venous pulse oximetry
